The mainstream technology in the field of gas sensors is to use a metal oxide semiconductor typified by tin dioxide (SnO2) as a gas detector and measure a change in electric resistance due to adsorption of chemical substances onto the surface of the metal oxide semiconductor material. To perform high-sensitive gas measurement under such configuration, electric current is supplied from a constant current source, while heating the gas sensor device up to a temperature suitable to achieving satisfactory detection characteristics. The power consumption of the detecting circuit thus tends to be high, and especially a large quantity of electric power is consumed by a heater for heating the gas sensor device.
There are some materials that can be, used for a resistive-type gas sensor operative at room temperature. Copper(I) bromide (with the formula CuBr, which is also called cuprous bromide), one of copper halides, is a typical example. A device using CuBr as a gas detector and exhibiting a significant change in electric resistance at room temperature, in the presence of ammonia in the air is proposed. See, for example, Analytica Chimica Acta, Vol. 515, PP. 279 (2004).
CuBr has excellent, characteristics in sensitivity and selectivity to ammonia. However, time for attaining the equilibrium representing the ammonia concentration from the initial state is as long as ten minutes, which means that it takes time for a sensor to respond to the change in resistance.
A technique or structure for maximizing the response speed of a gas sensor device using CuBr is desired.